Cloud storage is receiving increasing attention and importance recently. Cloud storage offers their users cost-effective, convenient and highly available storage services. Conventional clouds rely on cost-effective techniques such as data compression and data deduplication in order to save storage costs for the cloud. Data deduplication is beneficial as it significantly reduces the costs of storage. However, cloud users do not benefit from this deduplication, since deduplication is usually performed by the cloud itself. In other words users are usually being charged the same price, irrespective whether their data has been deduplicated by the cloud. This is a significant disadvantage for the users since users who are storing popular files which are usually deduplicated by the cloud storage should not be charged the same amount for storing non-deduplicated content.
In the non-patent literature of:    Pasquale Puzio, Refik Molva, Melek Onen and Sergio Loureiro. ClouDedup: Secure Deduplication with Encrypted Data for Cloud Storage, Proceedings of IEEE CloudCom 2013,    A Secure Data Deduplication Scheme for Cloud Storage, Jan Stanek, Alessandro Sorniotti, Elli Androulaki, and Lukas Kenc, Proceedings of Financial Cryptography and Data Security, 2014,    Boosting Efficiency and Security in Proof of Ownership for Deduplication, Roberto Di Pietro, Alessandro Sorniotti, Proceedings of ASIACCS 2012, and    Mihir Bellare and Sriram Keelveedhi, Thomas Ristenpart, DupLESS: Server-Aided Encryption for Deduplicated Storage, Proceedings of Usenix Security 2013,techniques are disclosed for performing deduplication over encrypted data or for a construction for a proof of ownership to attest that a user indeed possesses a file which is deduplicated by a cloud for example. These conventional techniques are directed to increase the profitability of clouds by allowing the cloud service provider to save on his storage costs.
However one of the disadvantages is, that these techniques are not transparent for the users of a cloud storage provider. A further disadvantage is, that such a cloud storage is costly for the users. An even further disadvantage is that users cannot verify if they are the only user of an uploaded file, or if other users also have uploaded the same file.